Recently I saw one of my centenarian patients, and I was impressed at how well she was doing, both physically and mentally. She is one of some 75,000 Americans living today over the age of 100. Just who lives long and healthy lives, and why?

Let’s start with genetics. It is true that those who come from long-lived families tend to live long as well. Some families are less likely to suffer from life-ending diseases like diabetes, cancer, and heart disease, and scientists have identified unique genetic traits strongly associated with longevity.

However, it is likely that our life span is determined by the combined effects of genetics and environmental factors. Studies of twins suggest that genetics may account for only about 20% to 30% of our chance of surviving to age 85.

Seventh Day Adventists, whose church encourages behaviors that promote healthy aging, have an average life span of 88 years, which is some eight years longer than average. Adventists exercise regularly, are vegetarian, don’t smoke, and don’t drink alcohol.

Personality helps to determine longevity. An eight-decade study out of Stanford University found that qualities of persistence, prudence, and being organized (and even obsessive) are associated with a long life; more so than qualities of being carefree, relaxed and laid-back. The theory is that conscientious people tend to make healthier choices, including who they marry, where they work, and whether they smoke, drive too fast, etc.

Diet does make a difference. Many centenarians live in the Mediterranean, where the average diet is high in fruit, vegetables, nuts, and olive oil. Studies confirm that the Mediterranean diet leads to an older age, less heart disease, and even protection against memory loss. Maintaining a healthy weight is important; obesity is rarely associated with a long life.

Studies show a correlation between education and a longer life. Those with a bachelor’s degree or higher live about nine years longer than do those who don’t graduate high school. The theory is that educated people get better jobs, plan for their future, and make healthier lifestyle choices.

Stress is not necessarily a bad thing. Productive, hardworking people are not automatically stressed and miserable, but often tend to be happier, healthier, and more socially connected than their less productive peers.

Life’s glitches happen to all of us. We all have bad days, weeks, and months, but most of the time the impact is temporary. Research shows that overreacting, constantly worrying, and living in a state of perpetual anxiety does indeed reduce life expectancy. It appears that it's not so much what happens to us, but how we deal with it, that really matters.

In a related matter, the popular concepts of mindfulness and meditation appear to play a role in longevity. Regular meditation has been shown to have a positive effect on anxiety and depression, which in turn can affect mortality. Meditation has been proven to bolster the immune system and reduce levels of cortisol, known as the stress hormone. Elevated levels of cortisol are linked to heart-related conditions, such as atherosclerosis and metabolic syndrome. It is not surprising when studies confirm that the mind is indeed connected to the body.

Building a community is important to living a longer life. Are you close to an extended family, or to a volunteer group, or to a religious community? Do you have a worthwhile career or positive educational goals? Interestingly, women appear to maintain stronger social networks, and are more likely to turn to friends, family and their community for support. That may be one reason why they tend to live longer than men. It’s long been recognized that married people tend to live longer than do their single friends.

Make sleep a priority. Getting enough quality sleep can reduce the risk of obesity, diabetes, heart disease, and mood disorders; and can speed recovery from illness.

Being sedentary is one of the biggest negative factors. Sitting for long periods of time puts us at risk for a number of health issues. A 2011 Australian study found that, after age 25, each hour spent sitting down and watching TV was linked to a loss of 22 minutes from overall life expectancy. Their findings suggest that watching too much TV is as detrimental to longevity as is smoking. I urge you to stay physically active in whatever way works best for you. Do anything but sit.

Make responsible life decisions. Wear a seat belt (it reduces the risk of death from car accidents by 50%!), wear a helmet while biking, protect yourself from sexually transmitted diseases, and avoid dangerous situations. Accidents are the third most common cause of death in the United States, and they are the main cause of death for those between the ages of 1 and 24. There is a very good reason why life insurance costs more for people who skydive.

Tobacco or other substance abuse? If your goal is a long and healthy life, then just forget about it. (Note that quitting smoking by the age of 30 can add up to 10 years to your life.)

Finally, bring something meaningful into your life. The Japanese concept of “ikigai” encourages us to keep busy with our own reasons for living. We all need a purpose to wake up for every morning; meaningful hobbies and activities may just lengthen our lives.

Most of these important components for a long and healthy life are obvious. Knowing about them is easy, but finding the path to following them is not. Sure, luck and genetics have a considerable impact on longevity, but your own efforts can add years to your life. Good luck with your journey to 100!

Dr. Alan Frischer is former chief of staff and former chief of medicine at Downey Regional Medical Center. Write to him in care of this newspaper at 8301 E. Florence Ave., Suite 100, Downey, CA 90240.